SMD LED LTW-C283DS5 Datasheet - 2.8x3.5mm Package - 3.2V Forward Voltage - White Light - 36mW Power - English Technical Documentation

1. Product Overview

The LTW-C283DS5 is a surface-mount device (SMD) LED lamp designed for automated printed circuit board (PCB) assembly. Its miniature form factor makes it suitable for space-constrained applications across a wide range of electronic equipment.

1.1 Core Advantages and Target Market

This LED features an ultra-thin 0.2 mm InGaN (Indium Gallium Nitride) white chip, delivering high brightness. It is compliant with RoHS (Restriction of Hazardous Substances) directives. The device is packaged on 8mm tape wound onto 7-inch diameter reels, conforming to EIA (Electronic Industries Alliance) standards, ensuring compatibility with high-speed automated pick-and-place equipment. Its design is also compatible with infrared (IR) reflow soldering processes, which is standard for modern PCB assembly lines.

The primary target markets include telecommunications equipment, office automation devices, home appliances, and industrial equipment. Specific applications encompass backlighting for keypads and keyboards, status indicators, micro-displays, and various signal and symbol lighting applications.

2. In-Depth Technical Parameter Analysis

The following section provides a detailed breakdown of the electrical, optical, and thermal specifications for the LTW-C283DS5 LED.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. They are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 36 mW. This is the maximum amount of power the LED can dissipate as heat.
• Peak Forward Current (I_F(PEAK)): 50 mA. This is the maximum allowable pulsed current, typically specified under conditions of a 1/10 duty cycle and a 0.1ms pulse width. It should not be used for continuous operation.
• DC Forward Current (I_F): 10 mA. This is the recommended maximum continuous forward current for reliable long-term operation.
• Operating Temperature Range: -20°C to +80°C. The device is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +85°C. The LED can be stored without damage within these limits.
• Infrared Soldering Condition: 260°C for 10 seconds. This defines the peak temperature and time profile the package can withstand during reflow soldering.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and a forward current (I_F) of 5mA, unless otherwise noted.

• Luminous Intensity (I_V): Ranges from a minimum of 112.0 mcd to a maximum of 280.0 mcd. The actual value is binned (categorized) as described in Section 4. Measurement is performed with a sensor and filter approximating the CIE photopic eye-response curve.
• Viewing Angle (2θ_1/2): 130 degrees. This is the full angle at which the luminous intensity is half of the peak intensity measured at 0 degrees (on-axis).
• Chromaticity Coordinates (x, y): Typical values are x=0.304, y=0.301 on the CIE 1931 chromaticity diagram. These coordinates define the white point of the emitted light and are also subject to a binning system.
• Forward Voltage (V_F): Ranges from 2.5V to 3.2V at I_F=5mA. The exact value is binned.
• Reverse Current (I_R): Maximum of 10 µA when a reverse voltage (V_R) of 5V is applied. It is critical to note that this parameter is for infrared (IR) test purposes only; the LED is not designed for operation under reverse bias.

2.3 Thermal Considerations

The power dissipation rating of 36 mW and the specified operating temperature range are key thermal parameters. Exceeding the maximum junction temperature, which is influenced by ambient temperature and forward current, can lead to reduced luminous output, accelerated degradation, and eventual failure. Proper PCB thermal design, including adequate copper pad area for heat sinking, is essential for maintaining performance and reliability, especially when operating near the maximum current rating.

3. Binning System Explanation

To ensure consistency in mass production, LEDs are sorted into bins based on key parameters. This allows designers to select parts that meet specific requirements for their application.

3.1 Forward Voltage (V_F) Binning

The forward voltage is categorized into seven bins (V1 to V7), each with a 0.1V range, from 2.5V-2.6V (V1) up to 3.1V-3.2V (V7). A tolerance of ±0.1V is applied to each bin. This is important for designing driver circuits and ensuring uniform brightness in arrays powered by a constant voltage source.

3.2 Luminous Intensity (I_V) Binning

The luminous output is divided into two primary bins:

• Bin R: 112.0 mcd to 180.0 mcd
• Bin S: 180.0 mcd to 280.0 mcd

A tolerance of ±15% is applied to each bin. The specific bin code is marked on the product packaging.

3.3 Hue (Chromaticity) Binning

The color of the white light is defined by its chromaticity coordinates (x, y) on the CIE 1931 diagram. The LTW-C283DS5 uses six hue bins (S1 through S6), each representing a specific quadrilateral region on the chromaticity chart. This binning ensures color consistency across multiple LEDs in an assembly. A tolerance of ±0.01 is applied to the (x, y) coordinates within each bin.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., typical forward current vs. forward voltage, relative luminous intensity vs. forward current, relative luminous intensity vs. ambient temperature), their trends can be described analytically.

The forward voltage (V_F) of an LED has a negative temperature coefficient; it decreases as the junction temperature increases. Conversely, the luminous intensity typically decreases as the junction temperature rises. For the InGaN white chip in this product, the light output can be expected to drop significantly if the maximum operating temperature is exceeded. The viewing angle characteristic shows a Lambertian or near-Lambertian distribution, with intensity being highest at 0 degrees and falling off towards the edges of the 130-degree cone.

5. Mechanical and Package Information

5.1 Package Dimensions

The LTW-C283DS5 utilizes a standard 2835 package footprint. The key dimensions are approximately 2.8mm in length and 3.5mm in width, with a height that includes the super-thin 0.2mm chip. All dimensional tolerances are ±0.1mm unless otherwise specified. The lens color is yellow, while the light source is an InGaN white chip.

5.2 Recommended PCB Attachment Pad and Polarity

A recommended land pattern (footprint) for the PCB is provided to ensure proper soldering and mechanical stability. The LED has anode and cathode terminals. The datasheet includes a diagram indicating the cathode marking, which is essential for correct orientation during assembly to ensure the device lights up when forward bias is applied.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

For lead-free (Pb-free) soldering processes, a specific reflow profile is recommended:

• Pre-heat Temperature: 150°C to 200°C.
• Pre-heat Time: Maximum of 120 seconds.
• Peak Temperature: Maximum of 260°C.
• Time at Peak Temperature: Maximum of 10 seconds. The LED should not be subjected to more than two reflow cycles.

It is emphasized that the optimal profile depends on the specific PCB design, solder paste, and oven used. Characterization for the specific application is advised.

6.2 Storage and Handling

Electrostatic Discharge (ESD) Precautions: The device is sensitive to ESD. Handling should be performed using wrist straps and anti-static gloves, with all equipment properly grounded.

Moisture Sensitivity: The LEDs are packaged in a moisture-barrier bag with desiccant. When sealed, they should be stored at ≤30°C and ≤90% relative humidity (RH) and used within one year. Once the bag is opened, the components are rated at Moisture Sensitivity Level (MSL) 3. They should be stored at ≤30°C and ≤60% RH and should undergo IR reflow within one week. If stored longer out of the original bag, a bake-out at 60°C for at least 20 hours is required before soldering to prevent \"popcorning\" damage during reflow.

6.3 Cleaning

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute is acceptable. Unspecified chemicals may damage the package material.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape with a width of 8mm. The tape is wound onto standard 7-inch (178mm) diameter reels. Each reel contains 5000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainder lots. The packaging conforms to ANSI/EIA-481 specifications.

8. Application Notes and Design Considerations

8.1 Typical Application Circuits

The LED is typically driven by a constant current source for optimal stability and longevity. A simple series resistor can be used with a constant voltage supply, where the resistor value R = (V_supply - V_F) / I_F. The chosen I_F must not exceed the maximum DC forward current of 10mA. For parallel arrays, individual current-limiting resistors for each LED are strongly recommended to compensate for V_F binning variations and prevent current hogging.

8.2 Thermal Management in Design

To maintain light output and lifespan, effective heat dissipation is crucial. Designers should use the recommended PCB pad layout, which often includes thermal relief connections to larger copper planes. Avoiding operation at the absolute maximum current and temperature ratings provides a reliability margin.

8.3 Application Limitations

The datasheet specifies that these LEDs are intended for ordinary electronic equipment. For applications requiring exceptional reliability, or where failure could jeopardize safety (e.g., aviation, medical life-support, transportation control), consultation with the manufacturer is required prior to use.

9. Technical Comparison and Positioning

The LTW-C283DS5 positions itself with several key differentiators: its ultra-thin 0.2mm chip enables lower profile designs compared to some standard LEDs. The use of an InGaN white chip typically offers higher efficiency and better color rendering than older technologies like phosphor-converted blue LEDs with different substrates. The 130-degree wide viewing angle makes it suitable for applications requiring broad illumination rather than a focused beam. Its full compatibility with automated SMT assembly and standard IR reflow processes aligns it with modern, cost-effective manufacturing workflows.

10. Frequently Asked Questions (FAQ)

Q1: What is the difference between the R and S luminous intensity bins?
A1: Bin R covers the range of 112-180 mcd, while Bin S covers 180-280 mcd at 5mA. Choosing Bin S guarantees higher minimum brightness.

Q2: Can I drive this LED with a 3.3V supply?
A2: Possibly, but it depends on the forward voltage (V_F) bin. For bins V6 (3.0-3.1V) and V7 (3.1-3.2V), a 3.3V supply may not provide sufficient voltage headroom for a series current-limiting resistor to operate effectively, especially considering tolerances. A dedicated constant-current LED driver or a higher supply voltage is often more reliable.

Q3: Why is the reverse current rating only for IR test?
A3: This specification is used during manufacturing testing. The LED's semiconductor junction is not designed to block significant reverse voltage. In application circuits, protection such as a parallel diode should be used if reverse voltage events are possible.

Q4: How critical is the 1-week floor life after opening the moisture barrier bag?
A4: For MSL 3 components, exceeding this time without a bake-out prior to reflow significantly increases the risk of internal package damage due to vapor pressure (popcorning) during the high-temperature soldering process, which can lead to immediate or latent failures.

11. Design and Usage Case Study

Scenario: Backlighting a Membrane Keypad. A designer needs to evenly illuminate 12 keys on a panel. They plan to use one LTW-C283DS5 LED per key, placed underneath a light guide. They select LEDs from Bin S for consistent, high brightness and from a single Hue bin (e.g., S3) to ensure uniform white color across all keys. The LEDs are driven in parallel from a 5V rail, each with its own 150Ω series resistor (resulting in I_F ≈ (5V - 2.9V)/150Ω ≈ 14mA, which is above the recommended 10mA maximum—highlighting a design error). A better design would use a 220Ω resistor for ~9.5mA or implement a constant-current driver array. The PCB layout follows the recommended pad pattern with thermal connections to a ground plane. The assembled board passes through a lead-free reflow oven using the specified profile, and the keypad provides uniform, bright backlighting.

12. Operational Principle

The LTW-C283DS5 is based on an InGaN (Indium Gallium Nitride) semiconductor chip. When a forward voltage exceeding the diode's threshold is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons—a process called electroluminescence. The specific composition of the InGaN alloy allows it to emit light in the blue/ultraviolet spectrum. To create white light, this primary emission is typically converted using a phosphor coating (likely contained within the yellow lens) which absorbs some of the blue light and re-emits it as yellow light. The combination of the remaining blue light and the phosphor-generated yellow light is perceived by the human eye as white.

13. Technology Trends

The solid-state lighting industry continues to evolve with several clear trends. There is a constant drive for higher luminous efficacy (more lumens per watt), which improves energy efficiency. Color rendering index (CRI) is becoming increasingly important, especially in display and architectural lighting, pushing for phosphor systems that produce more natural white light. Miniaturization remains key for portable and dense electronics, supporting the use of ultra-thin chips like the one in this product. Furthermore, integration is a trend, with LED packages incorporating drivers, sensors, or multiple color chips into single modules. Finally, reliability and longevity under higher operating currents and temperatures are areas of ongoing research and development.